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Level Streaming crash when using world composition


Our team is experiencing some pretty major crashing issues with level streaming in our open world game. We are using world composition. Our island has been split into 49 different levels in addition to other levels for caves or other things we decided to split up. We have been experiencing this crash for about a month now. Our first thought was to create a new Persistent level and see if the problem would go away. This seemed to have worked for about a week or so before we started crashing again. Below is the last crash log we received.

MachineId:2C2A7F424EBF4E294372EB9671AE52B3 EpicAccountId:5317144e63244d06832e99e93df21ae4

Unknown exception - code 00000001 (first/second chance not available)

Assertion failed: World->PersistentLevel [File:D:\BuildFarm\buildmachine_++depot+UE4-Releases+4.7\Engine\Source\Runtime\Engine\Private\LevelStreaming.cpp] [Line: 380] Most likely caused by reference to world of unloaded level and GC setting refe

KERNELBASE + 46045 bytes UE4Editor_Core!FOutputDeviceWindowsError::Serialize() + 292 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\windows\windowsplatformoutputdevices.cpp:95] UE4Editor_Core!FOutputDevice::Logf_VA() + 248 bytes [d:\buildfarm\buildmachine++depot+ue4-releases+4.7\engine\source\runtime\core\private\misc\outputdevice.cpp:144] UE4Editor_Core!FDebug::AssertFailed() + 1079 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\core\private\misc\outputdevice.cpp:224] UE4Editor_Engine!ULevelStreaming::RequestLevel() + 860 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\engine\private\levelstreaming.cpp:380] UE4Editor_Engine!UWorld::UpdateLevelStreamingInner() + 497 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\engine\private\world.cpp:2238] UE4Editor_Engine!UWorld::UpdateLevelStreaming() + 592 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\engine\private\world.cpp:2306] UE4Editor_Engine!UGameViewportClient::Draw() + 3865 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\engine\private\gameviewportclient.cpp:932] UE4Editor_Engine!FViewport::Draw() + 1223 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\engine\private\unrealclient.cpp:995] UE4Editor_UnrealEd!UEditorEngine::Tick() + 8339 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\unrealed\private\editor.cpp:1515] UE4Editor_UnrealEd!UUnrealEdEngine::Tick() + 22 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\editor\unrealed\private\unrealedengine.cpp:347] UE4Editor!FEngineLoop::Tick() + 4179 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\launchengineloop.cpp:2257] UE4Editor!GuardedMain() + 1404 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\launch.cpp:142] UE4Editor!GuardedMainWrapper() + 26 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\windows\launchwindows.cpp:126] UE4Editor!WinMain() + 249 bytes [d:\buildfarm\buildmachine_++depot+ue4-releases+4.7\engine\source\runtime\launch\private\windows\launchwindows.cpp:202] UE4Editor!__tmainCRTStartup() + 329 bytes [f:\dd\vctools\crt\crtw32\dllstuff\crtexe.c:618]

Product Version: UE 4.7
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asked Jun 09 '15 at 05:35 PM in Bug Reports

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avatar image Ben Halliday STAFF Jun 09 '15 at 06:33 PM

Hi joshezzell,

Level Streaming does not work with World Composition, and the crash is probably a result of this. Can you give me some details about how you set up your levels while World Composition was enabled? That should not have been possible. Or am I misunderstanding your setup?

Additionally, it would be helpful to see the log from the project when this crash occurred. You can find this in the project's Saved\Logs folder. Please zip and attach that here. Thanks!

avatar image joshezzell Jun 09 '15 at 06:57 PM

Hey Ben,

Right, it doesn't work with World Composition. This is what is slightly confusing about the issue. Early in development we were using level streaming instead of world comp. We switched to world comp and have since deleted all the level streaming volumes we created and the blueprint setups for them. Could there be an issues left behind from our earlier level streaming? Maybe something we did wrong?

avatar image ddvlost STAFF Jun 10 '15 at 02:15 AM


Just to clarify: world composition uses level streaming, but it does not support level streaming volumes.

About the crash: it caused by the fact that something holding a reference to a something in sub-level package. When it crashes it should print out reference chain into the log file. Could you attach one of the log files here?

avatar image Zaldir Jun 11 '15 at 06:08 PM

Didn't have the log file from that day, but 'produced' a new one, which is attached (along with dump files).

dreamtime.log (39.6 kB)
dumps.zip (131.6 kB)
avatar image ddvlost STAFF Jun 12 '15 at 10:51 AM

Looking at the logs I can't say for sure why it crashes. Looks like it happens when editor duplicates sub-level Landscape_3-4 for PIE session. Could you create an isolated project with persistent level and Landscape_3-4 and see if crashes on PIE start? We can then debug that project to find actual cause of the crash.

avatar image Zaldir Jun 19 '15 at 11:47 PM

Sorry about the late response. We've been a bit busy with the project. Josh is currently setting up that new project, but in the meantime, just to give you a better perspective of our crashes, I have included an image (of a tiny area of our world) showing where the crash occurs, and why I think it is unlikely that Landscape_3-4 is the (sole) culprit of our issue.


crash.jpg (506.6 kB)
avatar image ddvlost STAFF Jun 24 '15 at 10:47 AM

Could you temporally remove all foliage from all sub-levels and see if crash disappears?

avatar image Zaldir Jun 25 '15 at 09:44 PM

Temporarily removing the foliage seems to have fixed the issue for us. We have also found that while playing in the standalone window or a cooked game, it does not crash. Thus, this issue is not as critical as we first thought.

However, removing the foliage is not a permanent fix, so we will continue monitoring the issue.

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Hi Zaldir,

We haven't heard back from you about a test project in a while. Are you still experiencing this issue? If so, please upload the test project somewhere and reply with a link so we can take a look. Thanks!

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answered Jun 30 '15 at 05:37 PM

avatar image Zaldir Jun 30 '15 at 09:48 PM

I think we dropped working on the test project, when we could confirm that it was Landscape_3-4. And no, we are no longer experiencing the issue. Thank your assistance in the matter!

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